Photo-electric cell



Dec. 4, 1928 s. RUBEN PHOTO ELECTRIC CELL Filed Oct. 18, 1928 FIG. I.

FIG. 2.

M w R 0 H W Y 1 M W 1 u a a: A W x 1 l y C a T Patented Dec. 4, 1928.

SAMUEL RUBEN, OF NEW YORK, N. Y.

PHOTO-ELECTRIC onLL.

Continuation of application Serial No. 238,217, filed December 6, 1927.This application filed October This invention relates to aphoto-electric cell. The object of the invention is the provisionofcells of this type of high sensitivity.

This application constitutes a continuation of my copending applicationbearing Serial Number 238,217.

In my said prior application I described a photo-electric cell in whichthe electron emission from the cathode is controlled by photo-electricresponse to resistance changes of the photo-sensitive control element,the surface of which is composed of fused cuprous oxide. The oxide isroduced by heating a copper base in an oxi izing atmosphere andquenching it in hydrochloric acid to produce the desired 0 stallinestructure and also to reduce the sur ace layer of cupric oxide, afterwhich quenchin any undesirable byproducts of the reaction between thehydrochloric acid and the cuprous oxide is removed by mechanical orchemical means, such as immersion in a diluted nitric acid solution toassure a thoroughly cleansed surface. I have found that other compoundsare likewise photo-sensitive. I refer particularly to the compounds ofthe oxygen series in the sixth periodic group. These photosensitivematerials are such as molybdenum sulphide, silver sulphide, and silverselenides. I have also found that mixtures of oxides and sulphides, oroxides and selenides, or tellurides, can be made photo-electricallyresponsive. In all these materials it is important that the propercrystalline structure be obtained. This may be done by the methoddescribed in my said prior application, as by heating and causing areaction between the metal and a vapor of one of the elements named toproduce a surface of a photosensitive compound. Where a higherresistance is desired, instead of quenching, a very slow cooling can beemployed which permits the formation of large crystals. For someapplications the long crystal has advantages over the short one. Toproduce silver sulphide, a silver body of a proper form is heated in asulphur atmosphere and then heat treated to obtain the most eflicientcrystalline structure. is likewise treated. To produce selenides, aselenium vaporis used with the proper base material; it is likewise withrespect to tellurides. Where mixtures are desired they can MolybdenumSerial No. 313,369.

be applied in'thc form of a coating of finely ground crystals with asuitable binder which is volatilized so as to leave a residue that willnot cause too great a pressure effect in the evacuated tube.Particularly I have noted that the photosensitivity of conductivecrystalline compounds produced by a reaction with an element of theoxygen series compounds decreases with decreased electronegativecharacteristics or with the higher atomic numbers.

My invention then, consists of a photoelectric cell having threeelectrodes, a cathode, anode and grid, the last of which comprises ametal body having integrally formed on its surface a photo-sensitivecompound of the oxygen series in the sixth periodic group. In thisdevice, the grid is operated through the intermittent exposure of thesurface of the photo-sensitive compound to light rays, thereby varyingits electrical resistance and correspondingly, its potential employed tovary the distribution of the electron stream over the plate surface andtherefore the current flow in the cathode-anode circuit. The con-- trolelectrode or grid may be composed of copper or any other suitablyconductive metal base, having a suitably exposed surface of anintegrally formed homogeneous, non-porous, photo-sensitive compound ofthe oxygen series in the sixth periodic group.

Reference is made to the accompanying drawings of an embodiment of thisinvention in which, in Figs. 1, 2, and 3, the control elements aresurfaced respectively with cuprous oxide, silver sulphide and silverselenide, the other elements in the tube being, 1,

. a filamentary cathode coated with an alkaline earth oxide andsupported by leads 1, and 1 and anode 2, mounted on lead 2,. Thephotosensitive control element in the tube extends upon two sides of andparallel with the anode.

With the tube in operation, the cathodeanode current discharge is variedin response to changes in the external light rays impinging upon thephoto-sensitive grid coating.

What I claim is:

1. In a photo-electric cell, a control element comprising a copper bodyhaving integrally formed on its surface a photo-sensitive compound ofsaid body.

2. In a photo-electric cell, the combination of a cathode, an anode anda control electrode composed of a copper body having a surface of anintegrally formed, homogeneous, nonporous crystalline compound of saidcopper bod 3. In a photo-electric cell, a control element comprising ametal body having an exposed surface of a photo-sensitive coppercompound.

4. In a photo-electric cell a control element 10 comprising a metal bodyhaving formed on its surface a photo-sensitive compound of the oxygenseries of the sixth periodic group.

In testimony whereof, SAMUEL RUBEN has signed his name to thisspecification this 16th 15 day of October 1928.

SAMUEL RUBEN.

